Information display systems projected onto a pane which are reflected towards the driver or observer are known. These systems, also termed eye-level display systems, allow the driver of the vehicle to be informed, for example, of the speed of the vehicle without the driver having to look away from the field of view in front of the vehicle, and thus lead to an improvement in safety.
However, when an information item is projected onto a windscreen having a laminated structure composed of two glass sheets and an intermediate sheet of polymeric material, a double image is observed: a first image reflected by the surface of the windscreen facing the interior of the passenger compartment and a second image reflected from the external surface of the windscreen, these two images being slightly offset from one another. This offsetting can interfere with viewing the information.
To overcome this disadvantage there has been proposed, as described in U.S. Pat. No. 5,013,134, an eye-level display system using a laminated windscreen composed of two glass sheets and an intermediate layer of polyvinyl butyral (PVB), the two external faces of which are not parallel but are in a wedge-shape, with the result that the image projected by a display source and reflected by the face of the windscreen nearest the passenger compartment is virtually superimposed upon the same image originating from the same source reflected by the face of the windscreen towards the outside.
To construct this laminated pane having a wedge shape, an intermediate sheet having its thickness decreasing from the upper edge of the pane towards the lower edge is used. This solution, although satisfactory in terms of eliminating the double image, nevertheless has other disadvantages. In particular, the assembling of the laminated pane requires more stringent precautions, notably during its passage through a calenderer, because of the non-parallel faces of the two glass sheets. Furthermore, and in particular, the PVB can lose its initial thickness profile by flow or creep during assembly under pressure and heat which leads to poor results since the value and the uniformity of the decrease in the profile in the reflection zone are essential to this particular solution of the problem. Furthermore, with a laminated structure comprising two glass sheets it is not possible to create panes having a wedge shape over only a portion of their height, unless the face of the glass sheet towards the vehicle interior is machined, which is very difficult to carry out and almost impossible in the case of a curved glass sheet. The present invention eliminates the aforementioned disadvantages.